1. Field of the Invention
This invention relates to a foam fire extinguishing agent, more specifically, to an improved foam fire extinguishing agent having superior fire extinguishing properties, which generates foams with improved resistance to heat and oils.
Description of the Prior Art
Heretofore, various fire extinguishing agents such as a foam fire extinguishing agent, a powder fire extinguishing agent, an evaporable liquid fire extinguishing agent or a gaseous fire extinguishing agent have been used for fire control. These fire extinguishing agents have both advantages and disadvantages. For example, there have been suggested a foamable fire extinguishing agent comprising a foamable substance and an alkyl acid phosphate and a salt thereof (Japanese patent publication No. 35999/70) and an aqueous film forming foam composition comprising a fluoroalkyl-containing water-soluble compound (Japanese patent publication No. 20080/65).
However, these conventional fire extinguishing agents are not entirely satisfactory, although they, in fact, possess fire extinguishing properties. For example, in the fire extinguishing agent of the first-mentioned Japanese Patent Publication, a known surface active agent is used as the foamable substance. Since this surfactant itself is not easily miscible with other materials, the addition of additives to improve water-retention properties, resistance saturation by oil, fire resistance and stability of the foams, such as urea, lauryl alcohol, or metal salts, which have poor solubility, results in unstable fire extinguishing agents. Furthermore, such fire extinguishing agents do not possess entirely satisfactory fire resistance, oil resistance and re-ignition prevention capability.
The composition disclosed in the latter-mentioned Japanese Patent Publication, on the other hand, will prevent re-ignition, but since it must be used in amounts of about 0.3 to 1% by weight to water, it is expensive to manufacture. Further, this foam composition has little capability to control fires on combustible liquids having a low ignition point.